George Smith and Pat McCabe's hopes of playing for the Wallabies against the British and Irish Lions series remain alive after scans revealed their knee injuries were not as bad as first feared.

Champion openside flanker Smith has been diagnosed with a grade two medial ligament tear suffered in the Brumbies' 28-22 loss to the NSW Waratahs on Saturday night, meaning a best-case scenario could see him back on the park within six weeks.

That would give the 110-Test veteran just a slim hope of returning for an historic second crack at the Lions in the second Test in Melbourne on June 29.

However it is more likely Smith will miss the three-Test series and will not return to the field until the Brumbies' July 13 final-round Super Rugby fixture against the Western Force in Perth.

The news is better for Brumbies team-mate and Wallabies centre McCabe, who also incurred knee damage against the Waratahs on Saturday.

Scans showed no structural damage to McCabe's knee and he is expected to return for the Brumbies' May 31 clash against the Hurricanes in Canberra.

It will give McCabe just enough time to impress Wallabies coach Robbie Deans for one of the final six squad spots to be announced on June 11 for the Lions series.

The improved diagnosis for McCabe follows the announcement of his new contract with the Australian Rugby Union and the Brumbies that will take him through to the 2015 Rugby World Cup in England and Wales.